75. Sourcefire

Sourcefire sells software and services that help government and commercial organizations identify and address shortcomings in their networks’ cybersecurity protections. That line of business has become increasingly important as financial institutions, Web retailers and others have been the target of online attacks. John C. Burris, who had been the company’s chief executive since 2008, died of cancer in October.

Trivia

The founder of this company built the foundation of its security intelligence software on a dare over one weekend.